1. Field of the Invention
The present invention relates to an imaging apparatus, and more particularly to the printing section of an imaging apparatus having a duplex architecture.
2. Description of the Related Art
In an image forming apparatus, such as a laser printer, ink jet printer, copy machine or the like, often it is desirable to form an image on both sides of the substrates being printed. Printing on both sides, referred to as duplex printing, can create an impression of a more professionally prepared document, when appropriately bound, while also reducing file storage space requirements, media expense, shipping expenses and other handling expenses, particularly for long documents.
In a duplex printing operation, after an image is printed on a first side of the substrate, the substrate must be reversed in some fashion to present the opposite side of the substrate for printing. For proper appearance of a duplex printed document, the image on the second side should be positioned on the substrate similarly to the image on the first side of the substrate. That is, the top, bottom and side spacings should be the same on each side of the substrate, and both images should be properly aligned with the edges of the substrate. Numerous types of substrate reversal systems are known, including systems that merely turn the substrate over, as well as systems that reverse the substrate lengthwise and turn the substrate over. The image application procedure and substrate reversal system are selected so that the tops and bottoms of the images on both sides are in the desired relationship.
In today's world there is more and more focus on the economy especially in the area of paper usage. One example of this relates to the recent energy star regulations, in which any device that has a printing speed of ≧45 pages/minute must ship the duplexer included. The most popular duplex architecture is an internal design. This is effective in keeping the overall size of the device as small as possible.
There are two areas in which the internal duplex design has problems. First, they are not able to accommodate a wide range of media due to the tight turn radius of a paper path, the motor control design and the overall paper path length. For example, some printers can only support 16 to 28 pound plain paper and only in limited sizes. The second problem is that the performance of the printers drop off significantly in terms of sides/minute duplex which is much lower than pages/minute in the simplexed mode.
What is needed in the art is an internal duplex design that can support a wide range of media and provide improved performance cost effective manner.